Method of making thin flat electroded ceramic elements



July 3, 1956 CROOKS ETAL 2,752,662

METHOD OF MAKING THIN FLAT ELECTRODED CERAMIC ELEMENTS Filed Dec. 27, 1954 United States Patent METHOD OF MAKING THIN FLAT ELEC- TRODED CERAMIC ELEMENTS Marcius Lee Crooks and Pat A. Chefalo, signors to Erie Resistor Corporation, poration of Pennsylvania Application December 27,

Erie, Pa., as- Erie, Pa., a cor- 1954, Serial No. 477,888 2 Claims. (Cl. 2925 .35)

Ceramic phonograph pick-ups of polarized barium titanate ceramic and the like require thin flat ceramic elements which typically have a length of /8" and a thickness of from 8 to 10 mils. Such elements have heretofore been made by cutting from fired ceramic sheets of the finished mils).

the required flatness.

This invention is likewise intended to make the thin flat ceramic elements for phonograph pick-ups by cutting from fired ceramic sheets but instead sheets of from 8 to sliced off the ends of the ceramic bars, Fig. 4 is a perspective of one of the slices, and Fig. 5 is a greatly enlarged end view of a sandwich type pick-up made from two of the ceramic elements.

In Fig. 1 of the drawing is shown a ceramic phonograph pick-up element 1 which typically consists of a thin flat ceramic piece having, for example, a length of A", a width of /8" and a thickness of from 8 to 10 mils. As shown in the greatly enlarged cross sectional view in Fig. 5, the ceramic elements are used in pairs. Opposite faces of the ceramic elements are provided with ments are likely to be broken while being fastened together. It is diflicult to manufacture ceramic sheets of the required thinness and flatness. Although ceramic pick-up elements have been made for some time, the common method of manufacture is to cut the elements out of sheets having the thickness of the pick-up elements.

Instead of using thin ceramic sheets for making the ceramic elements, it is proposed to use relatively thick ceramic bars 4 having a Width 5 equal to the length 5a of the ceramic elements and a thickness 6 equal to the width 6a of the ceramic elements. The ceramic bars 4 are very easy to make and are much easier to handle than sheets having the thickness of the pick-up elements.

A suitable plastic is one of the solventof casting resins which has the out the evolution of gas. As soon as the plastic has set, the ceramic bars are firmly embedded in the plastic matrix.

In order to make the ceramic pick-up elements, a series of wafers 8 are cut off the ends of the matrix of plastic and ceramic bars, for example, by a diamond cut-off plastic. verse to the length of the ceramic bars width and thickness of he ceramic bars.

It will be noted that in the wafer 8, the ceramic elewith the plastic 7 and have their edges embedded in the plastic. The elements 1 are also spaced apart. To apply the electrode coatings 2 and 3 to the ceramic elements, the entire opposite faces of the wafer 8 (both the plastic and ceramic portions) are coated with metal, for example, by coating with one of the silver ceramic paints. Upon firing, the silver paint is set to opposite faces of the ceramic elements 1 and the plastic 7 disintegrates. If the opposite surfaces of the wafer 8 are coated by other metal coating processes in which the ceramic 7 is not disintegrated or burned away, the ceramic elements 1 with the metal coatings 2 and 3 thereon can be easily broken out of the plastic at the end of the metal coating operation.

What is claimed as new is:

1. The method of making thin fiat ceramic elements having a width and length much greater than the thickness and electroded on opposite faces, but not on the edges, which comprises casting into a matrix of settable plastic a plurality of fired ceramic bars side by side out of contact with each other, said bars having width and thickness corresponding respectively to the length and width of the ceramic elements, cutting flat wafers oif a thickness equal to the thickness of the ceramic elements by cuts transverse to the length and along the width and thickness directions of the ceramic bars embedded in the matrix, said wafers having flat surfaces flush with opposite faces of the ceramic elements embedded therein, coating both the plastic and ceramic portions of said opposite faces of the wafers with metal, and removing the metal coated ceramic elements from the Wafers.

2. The method of making thin flat ceramic elements having a width and length much greater than the thickness and electroded on opposite faces, but not on the 3 edges, which comprises casting into a matrix of settable plastic a plurality of fired ceramic bars side by side but out of contact with each other, said bars having width and thickness corresponding respectively to the length and width of the ceramic elements, cutting flat wafers oil the matrix of a thickness equal to the thickness of the ceramic elements by cuts transverse to the length and along the width and thickness directions of the ceramic bars embedded in the matrix, said Wafers having flat surfaces flush with opposite faces of the ceramic elements 4 embedded therein, coating both the plastic and ceramic portions of said opposite faces of the wafers with a metallic ceramic paint, and firing the wafers to set the paint to the ceramic elements and to disintegrate the plastic.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF MAKING THIN FLAT CERAMIC ELEMENTS HAVING A WIDTH AND LENGTH MUCH GREATER THAN THE THICKNESS AND ELECTRODED ON OPPOSITE FACES, BUT NOT ON THE EDGES, WHICH COMPRISES CASTING INTO A MATRIX OF SETTABLE PLASTIC A PLURALITY OF FIRED CERAMIC BARS SIDE BY SIDE OUT OF CONTACT WITH EACH OTHER, SAID BARS HAVING WIDTH AND THICKNESS CORRESPONDING RESPECTIVELY TO THE LENGTH AND WIDTH OF THE CERAMIC ELEMENTS, CUTTING FLAT WAFERS OFF THE MATRIX OF A THICKNESS EQUAL TO THE THICKNESS OF THE CERAMIC ELEMENTS BY CUTS TRANSVERSE TO THE LENGTH AND ALONG THE WIDTH AND THICKNESS DIRECTIONS OF THE CERAMIC BARS EMBEDDED IN THE MATRIX, SAID WAFERS HAVING FLAT SURFACES FLUSH WITH OPPOSITE FACES OF THE CERAMIC ELEMENTS EMBEDDED THEREIN, COATING BOTH THE PLASTIC AND CERAMIC PORTIONS OF SAID OPPOSITE FACES OF THE WAFERS WITH METAL, AND REMOVING THE METAL COATED CERAMIC ELEMENTS FROM THE WAFERS. 